EP3722375A1 - Paint system for intermediate sanding-free application on a wooden surface - Google Patents

Abstract

The invention relates to a paint system for application to a wood surface without any intermediate sanding. In order to provide a lacquer system, a method for producing a lacquer system and a use of such a lacquer system, which enable a significantly simplified and faster production process of a lacquered wooden workpiece and in particular no longer require intermediate sanding, which advantageously results in significant time and cost savings , it is provided that the paint system has at least one coating base with a binding agent and at least one salt that acts as a surface or wood surface smoother.

Description

The invention relates to a lacquer system for application to a wood surface without intermediate sanding, in particular to a wood surface that has only been roughly sanded and / or has not been primed. The invention also relates to a method for producing a paint system. Finally, the invention relates to the use of the lacquer system on a wood surface that has not been sanded between.

In the prior art, it is an established procedure for the production of lacquered wooden surfaces to carry out an intermediate lacquer sanding in order to remove fiber ends standing up from the wooden surface and thus to achieve a satisfactory result in the final lacquering, in particular with a transparent clear lacquer. In the prior art, intermediate sanding of the lacquer is always considered to be absolutely necessary in order to remove fiber ends that have come into contact with water or lacquer on the wood surface. Such an intermediate lacquer sanding or several sandings that are necessary in succession, however, lead to a long processing time and a great deal of effort in the production of lacquered wooden surfaces.

It is therefore an object of the present invention to provide a lacquer system, a method for producing a lacquer system and a use of such a lacquer system, which enable a significantly simplified and faster production process of a lacquered wooden workpiece and in particular no longer require intermediate sanding, which in an advantageous manner significant time and cost savings are achieved.

The object is achieved according to the invention by a paint system according to claim 1, a method according to claim 13 and within the scope of a use according to claim 14. Advantageous further developments of the invention are given in the dependent claims.

The paint system according to the invention for application to a wood surface without intermediate sanding, in particular to an only roughly sanded and / or unprimed wood surface, has at least one coating base comprising a binder and at least one salt that acts as a surface or wood surface smoother.

The method according to the invention for producing a lacquer system, in particular a lacquer system according to the invention, for inter-sand application to a wood surface comprises at least the process steps of producing a coating base comprising a binder and incorporating a salt that acts as a surface or wood surface smoother by dispersing, grinding or precipitating and thereby preferably using an agitator mill or a bead mill.

Furthermore, the invention comprises a use of a paint system, in particular a paint system according to the invention, for application to a non-sanded and / or in particular only roughly sanded and / or unprimed wood surface to produce a finished paint coating.

The invention has the advantage that it is surprisingly possible to deviate from the generally accepted principle that a wooden surface has to be sanded before painting or after a first layer of varnish has been varnished, in order to obtain a visually and haptically appealing wooden surface. A leading effect can be that the addition of a salt leads to a shift in the ion concentration gradient between the wood and the paint system to be applied, which results in an osmotic effect that significantly reduces or even completely prevents wood fibers from standing up on the surface of the wood to be painted .

The paint system can in principle be any paint system with any number of components. Basically, the paint system has at least one binder and can also contain filler, pigment, solvent, resin and / or additive or other auxiliaries. The paint system is preferably suitable for application with commercially available application systems and in particular for spray application, the processability of the being preferred by the addition of the salt according to the invention Paint system is not changed and in particular not restricted. Furthermore, the lacquer system is preferably already suitable for the final treatment and / or for the final lacquering of a wooden workpiece. It is particularly preferable for the wooden workpiece to be painted to be treated exclusively with the paint system, so that particularly preferably neither a primer nor a subsequent further painting is necessary. In addition, however, one or more, in particular transparent topcoat layers, in particular a high-gloss and / or particularly hard lacquer layer, can also be applied to the lacquer layer from the lacquer system according to the invention.

In principle, the lacquer system and / or the top lacquer can be formed from one or more layers that are identical to one another or differ in their composition. In addition, the lacquer system and / or the top lacquer can be transparent, translucent or opaque, with both a colorless and a colored design being conceivable. Finally, the lacquer system and / or the top lacquer can have any degree of gloss, in particular between dull matt and high gloss.

The paint system and in particular the binder in the paint system can have any chemical basis. For example, it can be a chemically crosslinking binder such as polyurethane or a radiation-crosslinking binder, in particular a UV-curing binder. Furthermore, the binder can be any synthetic resin, such as, for example, acrylate resin or alkyd resin, acrylate resin being preferred over alkyd resin. The binder can also be a one-component binder or a two-component binder (2K binder). This is preferably a chemically or reactively setting binder, although a radiation- or heat-hardening or acid-hardening binder or a physically drying binder, for example exclusively by solvent evaporation, is also conceivable.

Furthermore, the paint system can be solvent-free or have any solvent system, which, however, is preferably not water-based. The solvent preferably comprises n-butyl acetate, particularly preferably more than 20% and in particular too more than 50% of the total volume of the solvent. Very particular preference is given to using exclusively n-butyl acetate as the solvent. Alternatively, it is also possible to use a solvent mixture which preferably consists of n-butyl acetate as the main constituent and particularly preferably more than 90% of the volume or mass. Furthermore, the paint system can be used as a further solvent, for example acetone, in particular with a mass fraction of between 0.1% and 2%, and / or xylene, i.e. dimethylbenzene, in particular with a mass fraction between 0.1% and 2%, and / or methyl isobutyl ketone, in particular with a mass fraction between 0.1% and 5%. Alternatively, a solvent mixture of n-butyl acetate and methoxypropanol and, if necessary, small amounts of other solvents can be used, the ratio of n-butyl acetate to methoxypropanol preferably between 2: 1 and 1: 5, particularly preferably between 1: 1 and 1: 3 and very particularly preferably between 1.5: 2 and 1: 2.5 based on the masses. Finally, it is preferred that at least the main part of the solvent and particularly preferably all of the solvents contained are volatile constituents of the paint system and, accordingly, are essentially no longer contained in the cured paint.

An application without intermediate sanding is generally understood to mean an application of the paint system in one or more layers and / or work steps on a surface, in particular a wood surface, in which no sanding is carried out at least after the application of the first layer and particularly preferably also after the application of all subsequent layers the surface takes place. Due to the properties of the lacquer system according to the invention, such a sanding, in particular intermediate sanding, is no longer necessary, since the direct application of the lacquer system to the wood surface no longer leads to a strong raising of wood fiber ends.

Roughly sanded in the context of the invention means first of all that no sanding was carried out in order to sand off fine fiber ends which could subsequently stand up on the surface of the wood, in particular in the context of a lacquer finish. In addition, it is preferred that only a sanding of the wood surface with a grain size greater than 150, preferably greater than 120, particularly preferably greater than 100 and particularly preferably greater than 80, is necessary. Particularly preferably roughly ground means that im No wet sanding was carried out in the course of the surface preparation to remove the wood fibers that stand up.

An unprimed wood surface is understood to mean a wood surface that was not provided with an underlying coating that remained on the wood or was at least partially sanded off again before the paint system was applied. Particularly preferably, the lacquer system according to the invention can be used to dispense with a primer and subsequent intermediate sanding to remove wood fibers that stand up. Accordingly, the paint system can preferably be applied to a chemically untreated wood surface and / or without a primer. In addition, the lacquer system can also be applied directly to a bleached and / or stained wood surface, in particular without a previous coating.

In the method, the incorporation and in particular a dispersion of the salt in the paint system and in particular in the binder of the paint system is preferably carried out by means of an agitator mill, a bead mill, an air jet mill or a three-roller mill. It is preferred that the salt is distributed as finely as possible and / or as finely divided as possible and / or uniformly dispersed in order to achieve a uniform and good effect. Alternatively or additionally, the salt in the paint system can also be finely divided by precipitating the salt before the addition or directly in the paint system. In addition, the salt, which acts as a surface smoother or wood surface smoother, can also be added to a paint system as a salt concentrate, in particular a concentrate of fine-grained or precipitated salt.

The use of the lacquer system to produce a finished lacquer coating without intermediate sanding means in particular that the lacquer system can be applied directly to the wood surface in order to produce a lacquer or a lacquer layer that does not have to be sanded and / or painted over. Particularly preferably, the application of the lacquer system represents the final and complete lacquering of the wooden surface so that a completely lacquered wooden workpiece is obtained. Alternatively, one or more further topcoat layers are applied to the lacquer layer of the lacquer system according to the invention.

The surface or wood surface smoother can be formed from a single chemical substance or a mixture of substances. The subsurface or wood surface smoother is preferably formed exclusively from solids, in particular exclusively from salts. The basic task of the subfloor or wood surface smoothing machine is to reduce or even completely prevent wood fibers from standing up on or out of the surface of the wood to be varnished, so that varnishing without intermediate sanding is possible.

According to an advantageous further development of the paint system according to the invention, it is provided that the surface or wood surface smoother comprises an inorganic salt and is particularly preferably formed exclusively from one or more different inorganic salts, whereby a particularly simple and inexpensive production of the paint system with good storage stability can be achieved can. The salt preferably has an alkaline earth metal cation and / or a nitrate, a sulfate, a hydroxide or a halide as the anion.

According to a particularly advantageous development of the lacquer system according to the invention, the substrate or wood surface smoother comprises an alkali halide or an alkaline earth metal halide, in particular a potassium, magnesium and / or calcium halide, and particularly preferably the substrate or wood surface smoother is formed exclusively from them. Although in principle any alkaline earth metal halides are conceivable, a salt with potassium, magnesium or calcium cations and / or with fluoride, chloride or bromide anions is preferred.

A particularly advantageous development of the paint system according to the invention provides that the surface or wood surface smoother comprises calcium chloride, in particular calcium chloride dihydrate, and in particular is formed exclusively from it, which enables particularly favorable production with a particularly great effect at the same time. In principle, the salt of the subfloor or wood surface smoothing agent, and in particular the calcium chloride, can be hydrated or anhydrous as desired. Calcium chloride dihydrate is preferred, however, because it is not as hygroscopic as anhydrous calcium chloride and therefore leads to a better painting result and a more robust, water-unreactive paint surface. In addition, calcium chloride dihydrate is preferred over calcium chloride tetrahydrate and hexahydrate, since the dihydrate is cheaper and easier to process.

As an alternative or in addition, the surface or wood surface smoother can also comprise potassium chloride, in particular potassium chloride hexahydrate, and / or magnesium chloride, in particular magnesium chloride hexahydrate, and in particular be formed exclusively therefrom.

Since the surface or wooden surface smoother is supposed to have an osmotic effect, substances with strongly polar or electrovalent bonds are preferred. Strong ionic bonds are particularly preferred. Correspondingly, the subsurface or wood surface smoother is preferably a salt with an electronegativity difference between the cation and the anion or anions of at least 1.0, in particular at least 1.5 on the Pauling scale, the cation being particularly preferably an alkaline earth metal cation. The electronegativity of calcium is 1.00, magnesium 1.31 and chlorine 3.16 on the Pauling scale.

In order to achieve a particularly clear effect of the subsurface or wood surface smoother, it is advantageous if the subsurface or wood surface smoother is present as a salt that is dispersed and / or undissolved in the binder. In particular, this is also preferred, since in this way it can be prevented in a simple manner that the substrate or wood surface smoother reacts with other components already in the paint system or forms chemical, electrovalent or electrostatic bonds or causes effects. It is very particularly preferred that the entire paint system is water-free. Anhydrous is understood to mean the lacquer system if no water has been added and / or the water content is below 1%, preferably below 0.5%, particularly preferably below 0.25% and particularly preferably below 0.1% based on the chemicals used Total mass is.

In principle, the surface or wood surface smoother can be contained in the paint system in any concentration or with any mass fraction. The mass fraction is preferably used as a substrate or wood surface smoother active salt between 0.1% and 15%, preferably between 0.5% and 12%, particularly preferably between 1.5% and 10% and particularly preferably between 2% and 8% based on the total mass. A larger amount of salt in the composition, in particular more than 15% based on the total mass, leads to impaired optical properties and poor processability of the paint system. The minimum amount of salt to be used depends on the processing conditions as well as the wood to be varnished, whereby the residual moisture of the wood, the type of wood and the mechanical properties of the wood surface have an influence on the amount of salt required. The first effects could be observed from very low salt quantities of 0.1%, while a varnish system that can be used in a variety of ways requires a minimum salt quantity of around 1.5% based on the total mass of the paint system.

Although in principle any binder systems are conceivable, it is preferred that the binder comprises a two-component polyurethane system and, in particular, is essentially formed from it. The two components, in particular a synthetic resin base and a hardener, are particularly preferably mixed immediately before the use of the two-component paint system (2-component paint) in order to subsequently set through a chemical reaction. The binder or the lacquer system is in principle preferably a reactive lacquer, which particularly preferably forms a polyurethane (PUR) in the course of this chemical reaction. The addition of a hardener may be necessary in the paint system for subsequent processing or for coating a surface, whereby the hardener can only be added shortly before use and accordingly does not necessarily have to be part of the paint system or is a separate component of the paint system .

Accordingly, an embodiment of the paint system according to the invention is preferred in which the binder is formed from two components, the first component at least one hydroxy-functional polymer, preferably a polyol and particularly preferably an acrylic, polyester, urethane and / or epoxy polyol, and the salt as a substrate or wood surface smoother and optionally also an in particular anhydrous solvent and / or the second component is an isocyanate-based hardener, in particular a polyisocyanate, the two components in particular are preferably formed in such a way that the mixing ratio of the first and second components is between 2: 1 and 25: 1 gravimetric and / or volumetric, in particular 10: 1 volumetric.

In particular, an advantageous further development of the paint system according to the invention is preferred in which the first component is between 25% and 70% of one or more binders, in particular acrylic polyols, and / or between 5% and 15% of one or more polyester polyols and / or between 20% and 70% solvent and between 2% and 8% salt acting as a substrate or wood surface smoother based on the mass of the first component, with the 100% remaining preferably being auxiliaries, which are particularly preferably between 1% and 15% of the mass of the first component. The mass ratio between the first and the second component is preferably between 2: 1 and 25: 1, particularly preferably between 8: 1 and 12: 1 and particularly preferably about 10: 1.

The first component or the entire paint system preferably has a solvent content between 20% and 90%, particularly preferably between 30% and 80% and very particularly preferably between 50% and 70%, based on the total mass.

Particularly preferred is a composition of a basic formulation of the first component 64% of one or different acrylic polyols and 31% of one or more solvents and 4% of the salt that acts as a surface or wood surface smoother and 1% of auxiliaries and other substances, each based on the mass of the first component, fluctuations in the components of up to 2% being insignificant. The basic recipe is particularly preferably mixed with a commercially available and, in particular, water-free PUR paint in a mass ratio of 4: 1. Then a hardener is added and the lacquer is applied to the wood surface. Alternatively, the basic recipe can also be used directly without prior mixing with a PUR lacquer and mixed with a hardener.

The other substances contained in the paint system and in particular the auxiliaries can be selected as desired and in particular be additives that positively influence the properties of the paint system or a paint layer formed from the paint system. Such auxiliaries can be, for example, wetting and / or dispersing additives, in particular for stabilizing the salt in the paint system and possibly also for pigments contained in the paint and / or for increasing the storage stability. The mass fraction of the dispersing additive is preferably between 0.1% and 5%, particularly preferably between 0.5% and 2% and very particularly preferably about 1% of the total mass of the first component and / or of the entire paint system. Furthermore, a high molecular weight block copolymer, in particular with pigment- and / or salt-affine groups, and / or an Aerosil paste or silica, in particular pyrogenic silica, is preferably used as the dispersing additive.

To improve the paint surface, in particular to obtain a particularly smooth and / or scratch-resistant paint surface, further auxiliaries can be added, in particular suspensions of synthetic waxes (paraffins). The proportion of these auxiliaries which improve the paint surface is preferably between 0.1% and 5% of the total mass. Alternatively or additionally, a micronized synthetic wax can be contained to improve the surface properties, the proportion of the total mass preferably being between 0.01% and 0.5%.

Furthermore, any rheological auxiliaries can be contained in one or both components of the lacquer system, an auxiliary for increasing the viscosity at lower shear rates, particularly preferably a polyamide or polyurethane-wax dispersion or Aerosil being used for this. The proportion of rheological auxiliaries and in particular of the polyamide-wax dispersion is preferably between 0.05% and 1% based on the total mass.

It is also preferred to use at least one further binder with a significantly lower proportion in addition to the main binder.

In addition, a polyether-siloxane copolymer is preferably added in order to ensure a particularly flat surface in the finished paint layer. The proportion of the total mass is preferably between 0.01% and 0.5%.

According to a preferred development of the paint system according to the invention, this is Lacquer system formed in such a way that the lacquer layer formed during curing is translucent, in particular transparent, whereby the lacquered wood surface is particularly clearly visible and the function of the subsurface or wood surface smoother is particularly important, since the wood fibers that usually stand up on a transparently lacquered wood surface would not only be palpable, but also visible. Translucent generally means that the finished lacquer layer is at least translucent, but not necessarily transparent, while a transparent lacquer layer can be seen through unhindered.

Several exemplary embodiments of the paint system according to the invention and the method according to the invention are explained in more detail below.

In a first version of the paint system, a base coat made of 64% hydroxy acrylic resin or acrylic polyols in butyl acetate as a binder component, 11% n-butyl acetate and 20% methoxypropanol as a solvent, 1% of a dispersing additive in the form of a solution of high-molecular block copolymers with pigment - and salt-affine groups dissolved in xylene / butyl acetate / methoxypropyl acetate as well as 4% calcium chloride dihydrate produced as a substrate or wood surface smoother, all information being based on the total mass of the base coat.

The base coat is then mixed in a mass ratio of 80:20 with a commercially available lightfast and transparent multi-layer paint with a polyurethane-based binder system, in particular with HESSE PUR paint. In principle, however, it can also be used without prior mixing with such a layered lacquer. Furthermore, a hardener, preferably based on isocyanate and particularly preferably a HESSE PUR hardener, in particular in a volumetric ratio of 10: 1, is added to the mixture. The paint system can be processed with or without the addition of a thinner.

In order to obtain a varnished wooden surface, the finished wooden workpiece is varnished without prior sanding, the application quantity being 120-180 g / m ^{2, as} is usual in the PUR varnish sector. This is followed by drying for at least 2 hours at room temperature and varnishing without sanding with a gloss top coat, in particular a HESSE PUR lacquer in a volumetric mixing ratio of 10: 1 with a HESSE PUR hardener. Even after drying overnight (up to 16 hours), a result with good adhesion can be achieved.

In a further version of the paint system, in addition to 52% hydroxy acrylic resin or acrylic polyols in butyl acetate as a binder component, 16.5% n-butyl acetate as solvent, 0.8% of a dispersing additive in the form of a solution of high molecular weight block copolymers with pigment and Salt-affine groups dissolved in xylene / butyl acetate / methoxypropyl acetate to stabilize the salt in the paint system and to increase the storage stability, 8% of a polyester polyol in solvent as an additional binder and 6% calcium chloride dihydrate as a substrate or wood surface smoother added to the mixture numerous other auxiliaries, whereby all proportions are based on the total mass.

Other auxiliaries used include polyether siloxane copolymers with a mass fraction of about 0.1% based on the total mass, in order to avoid the formation of craters on the paint surface.

In order to obtain a particularly smooth and scratch-resistant paint surface, suspensions of synthetic waxes (paraffins) with a proportion of the total mass of about 2.6% are used. In addition, a micronized synthetic wax with a mass fraction of about 0.1% is added to improve the surface properties. The UV stabilizer contains a benzophenone UV absorber and diphenylmetanone with a mass fraction of about 0.01%.

In addition, a polyamide wax dispersion with a mass fraction of 0.2% is used to increase the viscosity at lower shear rates. To increase the flexibility of the polyurethane lacquer coating, slightly branched, hydroxy-containing polyesters are added as flexibilizers in a mass fraction of about 0.68%.

For the final processing, the mixture is then mixed in a volumetric mixing ratio of 10: 1 with an isocyanate-based hardener, in particular with HESSE PUR hardener, to form the workable product.

To produce a base coat, the components required above, in particular 64% hydroxyacrylic resin or acrylic polyols in butyl acetate as a binder component, 11% n-butyl acetate and / or 20% methoxypropanol as a solvent and 1% of a dispersing additive in the form of a Solution of high molecular weight block copolymers with pigment and salt-affine groups dissolved in xylene / butyl acetate / methoxypropyl acetate, weighed out, the percentages being based on proportions by mass. This mixture is then placed in an agitator mill, in particular in a bead mill, by means of which 4% calcium chloride dihydrate is subsequently homogeneously dispersed in this mixture as a substrate or wood surface smoother. Dispersion with glass beads is also possible on a laboratory scale.

The amount of calcium chloride dihydrate used of 4% based on the mass of the base coat was determined to be the optimal amount. Gradations of calcium chloride dihydrate with added amounts of 0% - 20% were carried out. The calcium chloride dihydrate also had to be incorporated in larger amounts, but with very high amounts of well over 10% added negative effects in the finished paint, such as strong cloudiness and greasy surfaces, occurred. Tests with other salts, in particular sodium chloride, ammonium polyphosphate and potassium carbonate, have not shown a satisfactory and / or a significantly poorer effect of these salts compared to calcium chloride as surface or wood surface smoother in a paint system, or they could not be dispersed sufficiently homogeneously in the paint system. In contrast, alkaline earth metal halides showed significantly better results.

Claims (14)

Lacquer system for application to a wooden surface without intermediate sanding, with - At least one coating base comprising a binder and - At least one salt that acts as a surface or wood surface smoother. Lacquer system according to Claim 1, characterized in that the surface or wood surface smoother is an inorganic salt. Lacquer system according to Claim 1 or 2, characterized in that the surface or wood surface smoother is an alkali halide or an alkaline earth metal halide. Paint system according to one of the preceding claims, characterized in that the surface or wood surface smoother is potassium chloride hexahydrate, magnesium chloride hexahydrate and / or calcium chloride dihydrate. Lacquer system according to one of the preceding claims, characterized in that the surface or wood surface smoother is a salt with an electronegativity difference of at least 2 on the Pauling scale. Lacquer system according to one of the preceding claims, characterized in that the surface or wood surface smoother is present as a salt dispersed and / or undissolved in the binder. Paint system according to one of the preceding claims, characterized in that the entire paint system is water-free. Paint system according to one of the preceding claims, characterized in that that the mass fraction of the salt that acts as a surface or wood surface smoother is between 1% and 10% based on the total mass. Lacquer system according to one of the preceding claims, characterized in that the binder is a two-component polyurethane system. Paint system according to one of the preceding claims, characterized in that the binder is formed from two components, the first component comprising at least one polyester polyol and the salt as a substrate or wood surface smoother and an anhydrous solvent and the second component an isocyanate-based hardener is. Lacquer system according to one of the preceding claims, characterized in that the first component contains between 50% and 70% acrylic polyols, between 20% and 40% solvent and between 2% and 8% salt, which acts as a surface or wood surface smoother, based on the mass of the first Component includes. Lacquer system according to one of the preceding claims, characterized in that the lacquer layer formed during curing is transparent. Method for producing a lacquer system for application to a wood surface without intermediate sanding, comprising the steps: - Production of a coating base comprising a binder and - Incorporation of a salt that acts as a substrate or wood surface smoother by dispersing, grinding or felling. Use of a paint system according to one of Claims 1 to 12 on a wood surface that has not been sanded in between, in particular only roughly sanded and / or unprimed, for producing a paint coating without sanding.